1. Field of the Invention
This invention relates to a solar heat collector having a vapor-impervious and moisture-impervious seal and the method of making same.
2. Discussion of the Technical Problems
The advantages of using solar heat collectors to collect solar energy for heating a fluid and/or for generating electric power have been recognized in the prior art.
In U.S. Pat. application Ser. No. 450,703 filed on Mar. 13, 1974, in the name of Pandit G. Patil and entitled "Solar Heat Collector" there is disclosed a solar heat collector having an outer cover plate, an intermediate cover plate and a solar energy and infrared absorber mounted in spaced relation to each other by spacer assemblies. Each of the spacer assemblies (1) maintains the cover plates and absorber in spaced relation to provide airspaces therebetween; (2) removes moisture from the airspaces and (3) prevents moisture from entering the airspaces.
Although the solar heat collector disclosed in the above-mentioned U.S. Pat. Application is ideally suitable for collecting solar radiation for subsequent use, the solar heat collector has limitations. For example, the spacer assembly preferably includes a moisture-impervious adhesive that prevents the moisture from entering the airspace. The moisture-impervious adhesives normally used in the art contain volatiles which are driven off at elevated temperatures, e.g., above 180.degree. F. (88.degree. C.).
During use of the solar heat collector, the collector is heated by solar radiation to temperatures of greater than about 200.degree. F. (93.degree. C.). At this temperature and above volatiles normally used in moisture-impervious adhesives are driven off and enter the airspaces. These volatiles have been found to condense on the cover plates and act as a barrier to solar radiation thereby reducing the efficiency of the solar heat collector.
In U.S. Pat. application Ser. No. 550,679 filed on Feb. 18, 1975, in the names of George H. Bowser, Renato J. Mazzoni and Lester F. Schutrum and entitled "Method of Fabricating a Solar Heat Collector" there is taught the step of heating the moisture-impervious adhesive prior to applying it to the peripheral edge portions of the solar collector. The adhesive is heated to a temperature higher than the expected temperature attained by the collector during use to drive out the volatiles in the adhesive.
It would be advantageous if other methods and solar collector designs were available that prevented or minimized the movement of the volatiles in the moisture-impervious adhesive into the compartments between the cover plates and absorber.